1. Field of the Invention
This invention relates generally to a source of alterative and environmentally clean energy, and in particular, to a system and method for extracting energy from ocean waves.
2. Description of the Prior Art
With increasing petroleum prices, political conflict, and the concern of global warming, there exists a growing world demand for alternative energy sources. It has been estimated that the total power of waves breaking on the world's coastlines at any given moment is between 2-3 terawatts. In favorable areas, such as environments typical of the west coast of the United States, Alaska, the north Atlantic coast, Canada, Europe, Australia, Hawaii, South Africa, and Chile, where the wave amplitude may reach 5-10 meters, wave power density may average 65 megawatts per mile of coastline. The barrel of oil equivalent is approximately 38 barrels of oil per hour per mile of coastline. By efficiently and economically harvesting wave energy, waves may provide a clean and unlimited energy source.
There have been attempts to tap into this unlimited energy source and make it economically viable. For example, U.S. Pat. No. 4,296,602 issued to Hales et al. and U.S. Pat. No. 4,137,005 issued to Comstock each disclose an elongate paddlewheel that has curved blades mounted about the diameter of the paddlewheel drums. Hales et al. and Comstock teach to orient the paddlewheels parallel to the wave front so that the force of an oncoming wave is received across the entire paddlewheel. Such an arrangement promotes the tendency of the paddlewheel to revolve with uneven speeds as a function of the periodic wave frequency, and it also tends to create reflected waves. U.S. Pat. No. 6,133,644 issued to Smith et al. discloses an elongate paddle having straight blading and oriented parallel with the oncoming waves for capturing wave kinetic energy. The straight blading is helically arranged about the paddlewheel. The Smith et al. device promotes continuous revolution of the paddlewheel and minimized wave reflections, but the device makes no provision for capturing potential energy of the waves. U.S. Pat. No. 6,935,832 issued to Platt et al. discloses a turbine device arranged for axial flow; due to its reduced footprint, such an arrangement is only exposed to a limited amount of wave power. Finally, European Patent Publication No. 384,757 in the name of Haleem, shows an elongate wave turbine that is oriented at an oblique angle to the wave front, which promotes continuous revolution of the drive shaft and minimizes wave reflections. Haleem discloses a device that is adapted to harness the potential energy of waves through the use of pivoting members on each blade. However, the complexity and large number of moving parts in the Haleem device increases its manufacturing and operating costs, particularly in the harsh ocean environment. It is desirable, therefore, to have a wave turbine that has a simple construction, that is efficient in capturing both wave kinetic and potential energies, and that is oriented at an oblique angle to the predominant wave fronts for promoting continuous revolution and for minimizing the creation of reflected waves.
Information pertaining to harvesting wave energy can be found in the following references, which are incorporated herein by reference:                Falnes, L. and Lovesethj. “Ocean Wave Energy”, Energy Policy, Vol. 19, No. 8, p. 768-775, 1991.        Hotta, H, et al. “On the Open Sea Test of a Prototype Device of a Floating Wave Power Device Mighty Whale”, Second European Wave Energy Conference, Lisbon, 1995.        Krogstad, Harold E. and Arntsen, Oivind A. “Linear Wave Theory” Part A, Trondheim Norway: Norwegian University of Science and Technology.        Krogstad, Harold E. and Arntsen, Oivind A. “Linear Wave Theory” Part A, Trondheim Norway: Norwegian University of Science and Technology.        Mollison, D. “Wave Climate and the Wave Power Resource”, in Hydrodynamics of Ocean Wave-Energy utilization, Evans and Falcao (eds), Springer-Verlag, pp. 133-156, 1986.        “New Re-View Quarterly Newsletter for the UK Renewable Energy Industry, Issue 43 February 2000.        P. White, 1989. “Developments in Norwegian Wave Energy”, Conference on Wave Energy Devices, Coventry, 1989.        World Energy Council. “Renewable Energy Resources: Opportunities and Constraints 1990-2020” 1993.        
3. Identification of Objects of the Invention
A primary object of the invention is to provide a wave turbine that simultaneously receives energy from multiple waves in a continuous fashion by use of a long wave turbine oriented at an oblique angle to the predominant wave fronts, with the blades offset from, and oriented at an oblique angle to, the shafting.
Another object of the invention is to provide a wave turbine that interacts with only a small portion of a wave front at any single moment in time so as not to significantly impede the flow of the wave.
Another object of the invention is to provide a wave turbine disposed essentially above the water level at a selectively adjustable elevation, for example, by the use of telescopic actuators at the pilings.
Another object of the invention is to provide a wave turbine with positively buoyant blades that capture both the wave's kinetic and potential (buoyant lifting) energies.
Another object of the invention is to provide a wave turbine that would minimize energy losses due to reflected waves.
Another object of the invention is to provide a system that compliments offshore wind farms for increasing the power generating capability thereof.
Another object of the invention is to provide a turbine having a low height profile that can be used to harvest energy from waves, river or tidal flow, or the wind without the use of tall blading.
Another object of the invention is to provide a turbine that minimizes hazards to marine and wild life.